tamerlan was charged in boating a former girlfriend. jahar began writing bizarre tweets. authorities never saw this coming. investigators are asking this morning, are there more cell members out there? that's the critical question, dan and bianna. >> pierre, a high level of security that there may be co-plotters out there. >> dan, think are trying to find out are there more people out there? so critical they talk to the younger brother who's still recovering from the injuries. they say they must find that out as quickly as possible. there's an international investigation under way to get to that subject. >>> time is of the essence, let's bring in george stephanopoulos, host of "this week." are they forced now to consider launch a military response? >> i think that's getting way ahead of ours, based on everything we know, even if there were accomplices, those accomplices were tied to a cell overseas to be identified and targeted. remember, they went back to russia, russia has been fighting these chechens separatts i think mitary action is not being contemplated here in any